Newspapers, magazines and print advertisers have seen the cost of their most basic commodity rise at double-digit rates since the Commerce Department began imposing the tariffs in March on Canadian imports, by far the publishing industry’s dominant paper source.

The result has been a kind of slow-motion breakdown for newspapers, long beset by declining ad revenue and disappearing readers. Even in an increasingly digital world, old-fashioned ink-on-paper remains the lifeblood of most newspapers. Print ads and subscriptions account for 75 percent or more of the revenue of an average daily newspaper. Newsprint is typically a publication’s second-biggest operating expense after labor.

And so rising paper prices have fallen like an ax throughout the news business:

The Tampa Bay Times in April cut 50 positions, or about 7 percent of its workforce, after projecting a $3 million increase in its newsprint budget, said chief executive Paul Tash. The paper also undertook economizing measures, such as reducing publication of a free tabloid paper from five days to just one day a week. “You might be able to absorb [higher costs] if the rest of the business was going swimmingly,” said Tash, “but this is a tough environment for newspapers.”

McClatchy Newspapers, publisher of the Miami Herald, Kansas City Star and more than two dozen other regional papers, on Tuesday laid off 3.5 percent of its workforce, or about 140 people. The layoff had several causes, but the company’s chief financial officer, Elaine Lintecum, said rising newsprint prices were a contributing factor. “You have to find a way to offset that,” she said.

The Pittsburgh Post-Gazette this week cut its print edition from seven days a week to five, eliminating Tuesday and Saturday publication. Editor David Shribman said the change was in the works for some time, saying: “We are emphasizing digital because the market is going digital.” But he added, “These tariffs aren’t helping us.”

(The Washington Post said its newsprint costs have risen 25 percent over the past year, but it has absorbed the costs without taking economizing measures).

Smaller papers are feeling the bite, too. The twice-weekly Storm Lake Times in Iowa (circulation 3,000) has seen its newsprint and printing bills rise by about 13 percent since the start of the year, according to Art Cullen, the paper’s editor. The Times, which won a Pulitzer Prize last year for editorial writing, is still running the same amount of copy, he said, but it has trimmed the size of its TV magazine, cut back on color printing and consolidated sections.

For Cullen, the newsprint crisis is just one battle in an ongoing war. “The real issue is the decline of rural communities and how that is sapping the small-newspaper industry,” he said. “What is harder to live with is knowing that the hardware store that closed used to run a quarter-page ad with you once a week and that the car dealers seem infatuated with Facebook,” he said. “We feel blessed to break even.”

The broader impact of the newsprint issue was laid out in a survey last month by the News Media Alliance, a trade group that is seeking to overturn the tariffs. Nearly half of the 272 newspaper publishers who responded to the survey said they had laid off staff as a direct result of newsprint price increases; some 71 percent said they had cut back the number of pages they published each day.

The organization said the publishers reported an average annual newsprint cost increase of $176,818 — a sum that could easily fund three or more newsroom jobs at many publications.

For many publishers, the price increase has been a double whammy. Advertisers that get their messages out via “preprints” — free-standing ad circulars distributed by newspapers — have also cut back as their costs have risen, further hurting publishers. The National Newspaper Association, a trade group whose membership is smaller dailies and weeklies, estimated last month that its members had seen a 20 percent reduction in preprints this year.

While the paper tariffs seem like a twofer for President Trump — a chance to protect domestic paper companies and a way to undermine the news media he has called “the enemy of the people” — there is no record of Trump raising the issue in public. Trump has been far more vocal about his desire for tariffs on foreign suppliers of other products, such as steel, aluminum and dairy.

The paper tariffs were imposed by the Commerce Department after the North Pacific Paper Co. (or NorPac) petitioned the agency for relief last summer. NorPac, based in Longview, Wash., argued that Canadian companies are subsidized by their government and injured American competitors by selling newsprint below cost, an unfair trading practice.

The Commerce Department investigated and found in NorPac’s favor; it began imposing higher duties on Canadian products in January (it reduced the duty on some products this month). In combination with a long decline among American suppliers — the demand for newsprint has shrunk steadily over the past two decades — this set newsprint prices on a sharp upward trajectory, said Paul Boyle, senior vice president of public policy at the News Media Alliance.

The tariffs have helped protect NorPac, which employs about 400 workers, but has set off widespread concern among publishers, who have few domestic sources of supply.

“We’re not seeking an advantage. We simply want a level playing field,” said David Richey, a NorPac spokesman. “We understand that newspaper publishers face a difficult marketplace, but high-quality local journalism should not rely on unfairly traded imports.”

Newspaper publishers have pinned their hopes for relief on two tracks, one legislative and one bureaucratic.

Legislation supported by publishers has been introduced in the Senate by Sen. Susan Collins (R-Maine) and in the House by Rep. Kristi L. Noem (R-S.D.) that would suspend the tariffs pending a study of their effects on the American economy. NorPac favors continuing the tariffs and opposes the legislation.

It is unclear, however, whether the measures have wide enough support to pass.

A more promising avenue, at least from Boyle’s perspective, may be the U.S. International Trade Commission, an independent federal agency that has the authority to modify or overturn the tariffs, pending a showing of harm to American industry.